function does not exist

CREATE FUNCTION myfunc(val NUMERIC)
RETURNS NUMERIC
BEGIN
    DECLARE in NUMERIC DEFAULT 0
    IF val=50000 THEN
        set in=1
    END IF
    RETURN in
END;

SELECT x.* FROM db_learn.public.individual_customer x
    JOIN (SELECT t.customer_rk, myfunc(t.monthly_income_amt) AS lwst FROM db_learn.public.individual_customer t 
    GROUP BY t.customer_rk HAVING myfunc(t.monthly_income_amt)=1) y
    ON y.customer_rk=x.customer_rk
LIMIT 50;

Ошибка : function myfunc(numeric) does not exist почему так?